The invention relates to a circuit arrangement for correcting the signals of a photoelectric image converter, which signals have been converted into digital form. Said image converter comprises a plurality of converter elements arranged in a row or area, especially for an image converter for performing precise brightness measurements.
Image converters of the mentioned type are, for example, required for taking pictures from satellites or aerial pictures, for taking thermograms, X-ray films and the like. The accuracy of the subsequent evaluation depends in this type of devices to a large degree on the characteristics of the individual converter elements of the image converter which are sequentially scanned. According to the present state of the art it is possible to manufacture at reasonable expense only photoelectric converters arranged in lineal or planar manner and having tolerances of .+-.5-10%. Stated differently, the individual converter elements differ from each other with regard to their dark signals and such saturation signals as well as with regard to the steepness of their characteristic curve and also with regard to variations of their converter characteristics which depend on time and temperature. Further sources of error in a precise radiation measurement of the object occur due to the light decrease or drop-off in the recording optical means and, where the object is artificially illuminated, the irregularity in the illumination also constitutes a source of error. These error sources have quite similar effects as the differing characteristic curves of the individual elements of the image converter.